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    <title>主窗口</title>
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         iframe {
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    <iframe id="ifr" src="./3. instanceOf2.html"></iframe>

    <script>
      var frame = window.frames[0];
      var isInstanceOf = [] instanceof frame.Array;
      console.log("frame.Array", frame.Array);
      console.log("isInstanceOf", isInstanceOf)

    </script>

</body>
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